The invention relates to a grounding plate for mounting in a telecommunications module, it also relates to a telecommunications module including one such grounding plate and a telecommunications rack-mounting system including such a module.
Transmission systems, with the aid of which data and voice signals are communicated at relatively high transmission rates, are finding increasing use in telecommunications. This makes it necessary to shield the components involved in transmission, i.e. both the individual cable cores as well as the modules, and more particularly the junction blocks terminating the cable cores, by suitable means so that the electromagnetic interference (EMI) protection requirements are satisfied. In this respect, it is especially important to shield cables forming a pair that comprise a shielding wire. At a junction module this shielding wire needs to be grounded to drop the voltages induced therein to ground.
DE 198 50 679 A1 discusses the case of a junction block for high transmission rates having the shielding wires of the individual pairs on the side contacts of the block. These side contacts connect to a relatively complicated grounding element which produces via side sections a conducting connection to sections of the rack-mounting system thereby connecting the shielding wires to ground. Experience has shown this solution may be a disadvantage in that the grounding elements are of relatively complicated design and the shielding wires terminate in a middle portion of the junction block so they need to be brought out to the side portions of the block which is a nuisance because it clutters and complicates the wiring of the junction block.
A junction and disconnecting block comprising a ground connecting element provided with what is called a xe2x80x9cprojecting memberxe2x80x9d for supporting, mounting and contacting the shielding of an incoming cable is discussed in EP 0 658 059 A1. So-called xe2x80x9cmultiple projecting membersxe2x80x9d are provided in its front portion for contacting shielding wires. In a rear portion, small tabs, to which separate resilient means for contacting the rack-mount are secured, are notched from a sheet-like grounding element. In this manner, the earth connecting element electrically contacts the rack-mount.
The invention is directed to providing a grounding element for comparatively cost-effective production permitting both an uncluttered and more reliable circuiting of a telecommunications module and safer grounding of the shielding wires of terminated pairs.
According to the invention, a contact section integrally formed with the grounding plate is provided on the rear portion of the grounding plate which serves to make contact with a telecommunications rack-mount. In one embodiment the grounding plate can be rack-mounted together with a telecommunications module so that the contact section is in contact with the troughed rack-mount. In this arrangement the configuration of the rack-mount or rack-mounting system can vary as long as it comprises one or more sections capable of electrically contacting the module at which the rear contact section of the grounding plate to electrically connect to the rack-mount. One such rack-mount may be provided as a rack-mount cross-section of practically any configuration, although it is preferred in this context that the cross-section is a relatively shallow xe2x80x9ctop-hatxe2x80x9d cross-section with the xe2x80x9chatxe2x80x9d open in a direction facing away from the module. The flat surface of the xe2x80x9chatxe2x80x9d forms the portion at which the rear contact section contacts the rack-mount.
Furthermore a troughed rack-mount may be provided, it being understood that a troughed rack-mount in this context comprises a rear wall or a rear section corresponding to the bottom of the xe2x80x9ctroughxe2x80x9d to which the rear side of a telecommunications module is fitted. Accordingly, also the rear portion of the grounding plate faces the bottom of the trough and the contact section can make contact with the trough by an extremely simple configuration of the grounding plate. In other words, the voltage induced in the shielding wires is now conducted via the contacts of the module to the contact fingers of the grounding plate, from which it is dropped to the rack-mounting system by particularly simple ways and means more or less in a straight line from front to rear via the contact section.
Generally, the grounding plate comprises a front portion and a rear portion. In its front portion, the grounding plate comprises several contact fingers, which are described in more detail below. In its rear portion, the grounding plate comprises the contact section, which is described above. As regards the contact section, it should be noted that any structure, which is adapted to contact a telecommunications rack-mount, is conceivable. In particular, the grounding plate can comprise, in its rear section, a suitable tab, finger or point extending from the rear section so as to perform the above-mentioned function. Furthermore, the rear edge of the grounding plate could be used as the contact section. Furthermore, the grounding plate can be practically flat so that it can be made by a simple stamping process with relatively few or no complicated angles. The only angled items can be relatively short tabs angled from the plane of the grounding plate to ensure reliable positioning of the grounding plate in a telecommunications module for certain applications.
The grounding plate is adapted for use with telecommunications modules in which the shielding wires of terminated pairs are connected to the xe2x80x9cusualxe2x80x9d contacts of the module. That means no separate shielding wire placement may be required to install the grounding plate. Instead, the individual contacts of the module are used (configured identical to the contacts terminating the regular cores to terminate the shielding wires of the pairs). In order to ground the shielding wires, the grounding plate can comprise several contact fingers in its front portion. Furthermore, the grounding plate can be mounted in or on a telecommunications module such that each of the individual contact fingers contacts a section of a module contact. More particularly, the contact fingers contact sections of the contacts provided for placing shielding wires.
xe2x80x9cFront portionxe2x80x9d in this context is understood to be the portion of the grounding plate that faces the side of the module where the contacts are located. The contact fingers are positioned on the grounding plate so that they contact the contacts provided for placing the shielding wires. This is why the grounding plate can be directly compatible with diverse module configurations. In other words, for a module on which contacts other than those as provided usually for placing the shielding wire, all that is needed now is to suitably adapt the positioning of the contact fingers on the grounding plate.
It is to be noted that the salient advantage afforded as compared to prior art is that a reliable dropping to ground is now achievable by a relatively simple and cost-effective component, whereas hitherto overvoltage protection magazines and links to connect the shielding wires to ground had to be used. These can be replaced by the invention. Since the number of contact points between separate elements can be minimized, and a simple, relatively flat grounding plate can be used, the transmission to ground is significantly improved. Furthermore the relatively flat grounding plate enhances the shielding effect and minimizes crosstalk between the two sides of a telecommunications module. In conclusion, the invention can be positioned in a module between the contacts of the module and its rear portion so that front access to the contacts of the module is not obstructed. Accordingly, placing and contacting jumper and test leads continues to be possible in the region of the contacts provided with shielding wires.
As already mentioned, the grounding plate can be relatively flat. However, in accordance with one preferred embodiment relatively short angled tabs are provided, particularly at side edges of the grounding plate, for positioning the grounding plate in or on the module. Preferably two angled tabs are provided on each side edge of the grounding plate. The tabs on each side extend in opposite directions from each other permitting the grounding plate to be reliably centered in a module containing one or more slotted opening(s) typically used for mounting an overvoltage protection magazine.
To correctly locate the grounding plate in or on the module it is good practice to provide at least one stop on the grounding plate.
For example, by providing at least one stop on the outline of the contact fingers.
To make contact between the contact section of the grounding plate and the troughed rack-mount it is good practice to provide a pointed projection on the contact section. The sharp edged tip can be used to scrape off any oxide film formed on the rack-mount. This achieves, especially when a turning action is involved in mounting a module grounding plate assembly in a rack-mounting system at least a slight scraping of the oxide film which lowers the contact resistance at this location. This turning action may be accomplished by latching the module first to one side of the rack mounting system before latching it to the other side so that the grounding plate is slightly turned about an axis perpendicular to the plane of the grounding plate and the contact section, more particularly with its pointed tip, covers a certain distance over the surface of the troughed rack-mount.
To ensure a snug contact of the contact section of the grounding plate with the troughed rack-mount and thus a safe electrical contact, it is good practice to provide a springy contact section that xe2x80x9cgivesxe2x80x9d slightly when in contact with the troughed rack-mount ensuring a good electrical contact. The springy property of the contact section can be achieved by providing a relatively narrow tab, which can lie in one plane with the grounding plate and extends from the rear portion of the grounding plate. Furthermore, a tab extending from the rear portion of the grounding plate can be stamped from the latter and bent in the direction extending distally from the rear portion of the grounding plate so as to form a contact section for contacting a rack-mount.
In this context it is preferred that a slot is provided in the vicinity of the contact section of the grounding plate. The slot can extend transversely to the direction extending from the front to the rear portion of the grounding plate, along the contact section, enabling the contact section to give, at least slightly, in a direction perpendicular to the elongation of the slot so that the contact section spring-contacts the troughed rack-mount. Preferably, the slot is located near the rear edge of the grounding plate, i.e. near the contact section so as to allow the contact section to xe2x80x9cgivexe2x80x9d when pressure is applied thereto.
A particularly advantageous embodiment of the grounding plate consists in it comprising, preferably at the above-mentioned angled tabs, supporting means for a printed circuit board. It is noted that the grounding plate displays its special advantages together with a telecommunications module which comprises at least one electronic component, in particular a splitter component provided on one or more printed circuit boards. The grounding plate can be used to advantage in such a module to support and fix in the module one or more printed circuit boards. For example, the supporting means can consist of either suitable latching or snap-action means into which a printed circuit board may be inserted or snapped.
It is advantageous to provide the grounding plate with one or more openings, apertures or slots, through which thick or tall electronic components can project. For example, relatively high electronic components provided on a printed circuit board which is supported by the grounding plate can be accommodated in such a slot. Since a fully completed or closed configuration of the grounding plate is not absolutely required in these areas for shielding purposes, an advantageous construction results from providing slots into which the electronic components of the printed circuit board extend. These slots are preferably located, in contrast to the slot on the outline of the contact section, at the xe2x80x9cinteriorxe2x80x9d of the grounding plate.
To prevent corrosion and to durably maintain the favorable springy response of the grounding plate in accordance with the invention it is good practice to make the grounding plate of stainless steel.
Although the grounding plate in accordance with the invention may be provided without a corresponding telecommunications module and it is suitable for retrofitting telecommunications modules, it is preferred to provide a fully-fitted module, more particularly a junction block, comprising a certain dimension with regard to the direction from the front to the rear portion already equipped with the grounding plate. In this arrangement, it is preferred that the grounding plate and the module equipped are adapted to each other such that the contact fingers of the grounding plate extend at least slightly into the contacts of the module. For example, the contact fingers may be inserted into a disconnecting, separating or isolating location existing on the contacts of the module. As mentioned, it is particularly advantageous if the module comprises at least one electronic component, e.g. a splitter component, on at least one printed circuit board.
Furthermore, existing rack-mounting systems can be retrofitted with modules in accordance with the invention. It is, however, preferred to provide a complete rack-mounting system together with several modules in accordance with the invention each equipped with the grounding plates to ensure optimum fit and electrical contact. In this arrangement, it is preferred that the grounding plate is the sole component ensuring electrical connection between the contacts of the module and the rack-mount. Accordingly, the grounding plate is preferably provided as a one-piece electrically conducting connection component between the contacts of a module and the rack-mount.